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System, method, and apparatus for control input prediction and state verification of fluidic vectoring exhaust in high performance aircraft

1. Technical Field

The present invention relates in general to directing the exhaust of an aircraft to improve its agility in flight and, in particular, to an improved system, method, and apparatus for control input prediction and state verification of a high performance aircraft's fluidic vectoring exhaust system.

2. Description of the Related Art

The exhaust nozzles of conventional jet aircraft typically direct the exhaust flow along a central axis of the nozzle. In order to improve the agility of high performance aircraft, vectoring nozzles have been used to redirect the exhaust slightly off-axis. Historically, vectoring nozzles have used mechanical systems to redirect the exhaust flow. Such mechanical systems usually employ plates or the like that are located adjacent to the nozzle to channel the exhaust flow in the desired direction. However, the need for aggressive next-generation designs with complex geometric shaping has placed an emphasis on moving away from mechanical systems.

One potential alternative to mechanical vectoring nozzles is fluidic vectoring nozzles. In contrast to most prior art designs, fluidic vectoring exhaust systems theoretically should not employ any mechanical moving parts to alter the direction of the exhaust plume, and therefore would have no physical surface deflection to measure and correlate to the desired vector state. Consequently, a significant problem encountered during the development of fluidic vectoring nozzles has centered on how to verify the vector state of the exhaust plume. An integrated flight control system would require both (1) a means for commanding a specific vector angle, and then (2) a means for verifying what vector angle resulted (i.e., feedback) to allow corrections so that the desired vector angle is actually produced. Thus, a solution for fluidic thrust vectoring exhaust systems that is non-intrusive and encompasses an exhaust vector state input prediction and verification scheme that can be implemented in a flight control system would be desirable.

One embodiment of a system, method, and apparatus for control input prediction and state verification of an aircraft's fluidic vectoring exhaust is disclosed. The invention predicts inputs required to produce a vectored state (e.g., pitch, yaw, etc.) and then verifies the resulting vectored state actually produced in a fluidic vectoring nozzle. The first step in the scheme is prediction of the fluidic control input needed to produce a desired vector state of the exhaust plume. For example, when an aircraft flight control system determines the need for a specific vector state, it utilizes a prediction method for determining the injected flow inputs required to obtain the desired vector state. After these inputs are commanded, a feedback loop is necessary to relay back to the control system the vector state that was actually produced.

The input prediction may be based on vectoring test data, high fidelity computational fluid dynamics (CFD) analysis, or other methods known to those skilled in the art. A correlation is derived between thrust vector state and ratios of injected flow pressure to nozzle flow pressure, and of nozzle flow pressure to local atmospheric pressure. When a given thrust vector angle is commanded, the injected flow pressure is adjusted to the corresponding pressure indicated by the pressure ratio correlations.

The vectored state verification of the fixed nozzle's exhaust plume is derived from nozzle wall pressures and a correlation factor that was derived by looking at a control volume encompassing the exhaust system. The control volume encompassing the fluidic nozzle yields known inflow characteristics, and pressure changes (ΔP) multiplied by area segments (ΔPdA) on the nozzle walls and exit conditions. During vectoring conditions the ΔPdA is non-zero because the injected flow changes the pressure distribution on the nozzle walls.

Through the use of vectoring test data or CFD, a direct correlation between nozzle wall pressures and vector angle is established. In addition, the ratio of the vector angle to a function of the nozzle wall pressures is constant at given ratios of nozzle pressure to ambient pressure. As a result, a direct correlation between the nozzle wall pressures and vector angle is established.

Overall, the control system derives a desired vector state, then predicts and sets the fluidic injection input required to produce the desired vector state. Finally, a vectored state verification routine is used to determine the resulting vector state for feedback to the control system. The invention offers a robust solution that accomplishes a mechanically non-invasive, fluidic nozzle vector control in a next generation, advanced nozzle configuration. In addition, the feedback feature allows compensation for valve wear, leakage, etc.

The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the present invention, taken in conjunction with the appended claims and the accompanying drawings.

So that the manner in which the features and advantages of the present invention, which will become apparent, are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof that are illustrated in the appended drawings which form a part of this specification. It is to be noted, however, that the drawings illustrate only some embodiments of the invention and therefore are not to be considered limiting of its scope as the invention may admit to other equally effective embodiments.

FIG. 1 is an isometric view of one embodiment of an aircraft constructed in accordance with the present invention;

FIG. 2 is an isometric view of one embodiment of a fluidic vectoring system for the aircraft of FIG. 1 and is constructed in accordance with the present invention;

FIG. 3 is a schematic plan view of a portion of the fluidic vectoring system of FIG. 2 and is constructed in accordance with the present invention; and

FIG. 4 is a high level flow diagram of one embodiment of a method constructed in accordance with the present invention.